package scheduler

import (
	"context"
	"errors"
	"sync"
	"testing"
	"time"

	"github.com/google/uuid"
	"github.com/prometheus/client_golang/prometheus/testutil"

	"github.com/vasyakrg/dns-autoresolver/internal/diff"
	"github.com/vasyakrg/dns-autoresolver/internal/metrics"
	"github.com/vasyakrg/dns-autoresolver/internal/notify"
	"github.com/vasyakrg/dns-autoresolver/internal/store"
)

// mockStore is an in-memory SchedStore double.
type mockStore struct {
	mu sync.Mutex

	schedules []store.Schedule
	domains   map[uuid.UUID][]store.Domain
	status    map[uuid.UUID]string

	touchedProjects []uuid.UUID

	// driftCount is what CountDriftDomains returns — a canned system-wide
	// count, independent of what this RunOnce's due projects touched.
	driftCount int
}

func newMockStore() *mockStore {
	return &mockStore{
		domains: make(map[uuid.UUID][]store.Domain),
		status:  make(map[uuid.UUID]string),
	}
}

func (m *mockStore) ListDueSchedules(ctx context.Context, now time.Time) ([]store.Schedule, error) {
	return m.schedules, nil
}

func (m *mockStore) TouchScheduleRun(ctx context.Context, projectID uuid.UUID, at time.Time) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.touchedProjects = append(m.touchedProjects, projectID)
	return nil
}

func (m *mockStore) ListDomains(ctx context.Context, projectID uuid.UUID) ([]store.Domain, error) {
	return m.domains[projectID], nil
}

func (m *mockStore) GetDomainStatus(ctx context.Context, domainID uuid.UUID) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if st, ok := m.status[domainID]; ok {
		return st, nil
	}
	return StatusUnknown, nil
}

func (m *mockStore) SetDomainStatus(ctx context.Context, domainID uuid.UUID, status string) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.status[domainID] = status
	return nil
}

func (m *mockStore) CountDriftDomains(ctx context.Context) (int, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.driftCount, nil
}

// mockChecker returns a preset Changeset or error per domainID, and records
// which domain IDs it was called with.
type mockChecker struct {
	mu      sync.Mutex
	results map[uuid.UUID]diff.Changeset
	errs    map[uuid.UUID]error
	calls   []uuid.UUID
}

func (c *mockChecker) Check(ctx context.Context, projectID, domainID uuid.UUID) (diff.Changeset, error) {
	c.mu.Lock()
	c.calls = append(c.calls, domainID)
	c.mu.Unlock()
	if err, ok := c.errs[domainID]; ok {
		return diff.Changeset{}, err
	}
	return c.results[domainID], nil
}

// mockNotifier records every Event it is asked to Send, and returns a
// canned set of per-channel results (results defaults to nil, i.e. no
// channels) so tests can assert on scheduler.checkDomain's per-channel
// metric recording.
type mockNotifier struct {
	mu      sync.Mutex
	events  []notify.Event
	results []notify.ChannelResult
}

func (n *mockNotifier) Send(ctx context.Context, projectID uuid.UUID, ev notify.Event) ([]notify.ChannelResult, error) {
	n.mu.Lock()
	defer n.mu.Unlock()
	n.events = append(n.events, ev)
	return n.results, nil
}

func (n *mockNotifier) count() int {
	n.mu.Lock()
	defer n.mu.Unlock()
	return len(n.events)
}

func driftChangeset() diff.Changeset {
	return diff.Changeset{Diffs: []diff.RecordDiff{{Kind: diff.Update, Name: "www"}}}
}

func TestRunOnce_NotifiesOnDriftNotOnFirstInSync(t *testing.T) {
	projectID := uuid.New()
	templateID := uuid.New()
	domainA := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: &templateID}
	domainB := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: &templateID}

	st := newMockStore()
	st.schedules = []store.Schedule{{ID: uuid.New(), ProjectID: projectID, IntervalSeconds: 3600, Enabled: true}}
	st.domains[projectID] = []store.Domain{domainA, domainB}

	checker := &mockChecker{
		results: map[uuid.UUID]diff.Changeset{
			domainA.ID: driftChangeset(),
			domainB.ID: {},
		},
	}
	notifier := &mockNotifier{}
	m := metrics.New()

	// CountDriftDomains is the real system-wide count, independent of what
	// this tick touched — set it to something that would NOT match a local
	// per-tick accumulator (only 1 of 2 domains here drifted) to prove the
	// gauge comes from the store call, not a local tally.
	st.driftCount = 7

	sched := New(st, checker, notifier, m)

	if err := sched.RunOnce(context.Background(), time.Now()); err != nil {
		t.Fatalf("RunOnce: %v", err)
	}

	if st.status[domainA.ID] != StatusDrift {
		t.Fatalf("domain A status = %q, want drift", st.status[domainA.ID])
	}
	if st.status[domainB.ID] != StatusInSync {
		t.Fatalf("domain B status = %q, want in_sync", st.status[domainB.ID])
	}

	if got := notifier.count(); got != 1 {
		t.Fatalf("notifications sent = %d, want 1 (only domain A)", got)
	}
	if notifier.events[0].Domain != domainA.ID.String() {
		t.Fatalf("notified domain = %q, want domain A (%s)", notifier.events[0].Domain, domainA.ID)
	}
	if notifier.events[0].Status != StatusDrift {
		t.Fatalf("notified status = %q, want drift", notifier.events[0].Status)
	}

	if len(st.touchedProjects) != 1 || st.touchedProjects[0] != projectID {
		t.Fatalf("TouchScheduleRun calls = %v, want [%s]", st.touchedProjects, projectID)
	}

	if got := testutil.ToFloat64(m.ChecksTotal.WithLabelValues(StatusDrift)); got != 1 {
		t.Fatalf("ChecksTotal{drift} = %v, want 1", got)
	}
	if got := testutil.ToFloat64(m.ChecksTotal.WithLabelValues(StatusInSync)); got != 1 {
		t.Fatalf("ChecksTotal{in_sync} = %v, want 1", got)
	}
	if got := testutil.ToFloat64(m.DriftDomains); got != float64(st.driftCount) {
		t.Fatalf("DriftDomains gauge = %v, want %d (from CountDriftDomains)", got, st.driftCount)
	}
}

func TestRunOnce_Idempotent_NoRepeatNotifyOnUnchangedDrift(t *testing.T) {
	projectID := uuid.New()
	templateID := uuid.New()
	domainA := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: &templateID}

	st := newMockStore()
	st.schedules = []store.Schedule{{ID: uuid.New(), ProjectID: projectID, IntervalSeconds: 3600, Enabled: true}}
	st.domains[projectID] = []store.Domain{domainA}

	checker := &mockChecker{
		results: map[uuid.UUID]diff.Changeset{domainA.ID: driftChangeset()},
	}
	notifier := &mockNotifier{}
	m := metrics.New()
	sched := New(st, checker, notifier, m)

	if err := sched.RunOnce(context.Background(), time.Now()); err != nil {
		t.Fatalf("first RunOnce: %v", err)
	}
	if got := notifier.count(); got != 1 {
		t.Fatalf("after first run notifications = %d, want 1", got)
	}

	if err := sched.RunOnce(context.Background(), time.Now()); err != nil {
		t.Fatalf("second RunOnce: %v", err)
	}
	if got := notifier.count(); got != 1 {
		t.Fatalf("after second run (drift->drift) notifications = %d, want still 1 (no repeat)", got)
	}
}

func TestRunOnce_CheckError_StatusErrorAndNotify(t *testing.T) {
	projectID := uuid.New()
	templateID := uuid.New()
	domainA := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: &templateID}

	st := newMockStore()
	st.schedules = []store.Schedule{{ID: uuid.New(), ProjectID: projectID, IntervalSeconds: 3600, Enabled: true}}
	st.domains[projectID] = []store.Domain{domainA}

	checker := &mockChecker{
		errs: map[uuid.UUID]error{domainA.ID: errors.New("provider timeout")},
	}
	notifier := &mockNotifier{}
	m := metrics.New()
	sched := New(st, checker, notifier, m)

	if err := sched.RunOnce(context.Background(), time.Now()); err != nil {
		t.Fatalf("RunOnce: %v", err)
	}

	if st.status[domainA.ID] != StatusError {
		t.Fatalf("domain A status = %q, want error", st.status[domainA.ID])
	}
	if got := notifier.count(); got != 1 {
		t.Fatalf("notifications = %d, want 1 (unknown->error)", got)
	}
	if notifier.events[0].Status != StatusError {
		t.Fatalf("notified status = %q, want error", notifier.events[0].Status)
	}
	if got := testutil.ToFloat64(m.ChecksTotal.WithLabelValues(StatusError)); got != 1 {
		t.Fatalf("ChecksTotal{error} = %v, want 1", got)
	}
}

func TestRunOnce_SkipsDomainWithoutTemplate(t *testing.T) {
	projectID := uuid.New()
	templateID := uuid.New()
	domainNoTemplate := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: nil}
	domainWithTemplate := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: &templateID}

	st := newMockStore()
	st.schedules = []store.Schedule{{ID: uuid.New(), ProjectID: projectID, IntervalSeconds: 3600, Enabled: true}}
	st.domains[projectID] = []store.Domain{domainNoTemplate, domainWithTemplate}

	checker := &mockChecker{
		results: map[uuid.UUID]diff.Changeset{domainWithTemplate.ID: {}},
	}
	notifier := &mockNotifier{}
	m := metrics.New()
	sched := New(st, checker, notifier, m)

	if err := sched.RunOnce(context.Background(), time.Now()); err != nil {
		t.Fatalf("RunOnce: %v", err)
	}

	for _, id := range checker.calls {
		if id == domainNoTemplate.ID {
			t.Fatalf("Checker.Check was called for templateless domain %s, want skipped", id)
		}
	}
	if len(checker.calls) != 1 || checker.calls[0] != domainWithTemplate.ID {
		t.Fatalf("Checker.Check calls = %v, want exactly [%s]", checker.calls, domainWithTemplate.ID)
	}

	if _, ok := st.status[domainNoTemplate.ID]; ok {
		t.Fatalf("templateless domain status = %q, want no status set (never checked)", st.status[domainNoTemplate.ID])
	}
	if st.status[domainWithTemplate.ID] != StatusInSync {
		t.Fatalf("domain with template status = %q, want in_sync", st.status[domainWithTemplate.ID])
	}

	if got := notifier.count(); got != 0 {
		t.Fatalf("notifications sent = %d, want 0 (templateless skip is silent, and template domain unknown->in_sync is not news)", got)
	}

	if got := testutil.ToFloat64(m.ChecksTotal.WithLabelValues(StatusInSync)); got != 1 {
		t.Fatalf("ChecksTotal{in_sync} = %v, want 1 (only the templated domain was checked)", got)
	}
}

// TestRunOnce_RecordsPerChannelNotificationMetrics exercises the fix for the
// "IncNotification('dispatch', newStatus) unconditionally" bug: the
// scheduler must record one NotificationsTotal increment per channel result,
// labeled by that channel's actual type and its actual sent/failed outcome
// — not a single "dispatch" placeholder blind to per-channel delivery.
func TestRunOnce_RecordsPerChannelNotificationMetrics(t *testing.T) {
	projectID := uuid.New()
	templateID := uuid.New()
	domainA := store.Domain{ID: uuid.New(), ProjectID: projectID, TemplateID: &templateID}

	st := newMockStore()
	st.schedules = []store.Schedule{{ID: uuid.New(), ProjectID: projectID, IntervalSeconds: 3600, Enabled: true}}
	st.domains[projectID] = []store.Domain{domainA}

	checker := &mockChecker{
		results: map[uuid.UUID]diff.Changeset{domainA.ID: driftChangeset()},
	}
	notifier := &mockNotifier{
		results: []notify.ChannelResult{
			{Type: "telegram"},
			{Type: "webhook", Err: errors.New("x")},
		},
	}
	m := metrics.New()
	sched := New(st, checker, notifier, m)

	// unknown -> drift: shouldNotify is true, so notifier.Send fires once.
	if err := sched.RunOnce(context.Background(), time.Now()); err != nil {
		t.Fatalf("RunOnce: %v", err)
	}

	if got := testutil.ToFloat64(m.NotificationsTotal.WithLabelValues("telegram", "sent")); got != 1 {
		t.Fatalf("NotificationsTotal{telegram,sent} = %v, want 1", got)
	}
	if got := testutil.ToFloat64(m.NotificationsTotal.WithLabelValues("webhook", "failed")); got != 1 {
		t.Fatalf("NotificationsTotal{webhook,failed} = %v, want 1", got)
	}
}

func TestShouldNotify(t *testing.T) {
	cases := []struct {
		name string
		prev string
		new  string
		want bool
	}{
		{"unknown->drift notifies", StatusUnknown, StatusDrift, true},
		{"unknown->error notifies", StatusUnknown, StatusError, true},
		{"unknown->in_sync is silent (first sync is not news)", StatusUnknown, StatusInSync, false},
		{"drift->drift does not repeat", StatusDrift, StatusDrift, false},
		{"error->error does not repeat", StatusError, StatusError, false},
		{"drift->in_sync notifies (resolved)", StatusDrift, StatusInSync, true},
		{"in_sync->drift notifies", StatusInSync, StatusDrift, true},
		{"in_sync->error notifies", StatusInSync, StatusError, true},
		{"in_sync->in_sync is silent", StatusInSync, StatusInSync, false},
		{"error->drift notifies (still bad, different bad)", StatusError, StatusDrift, true},
		{"error->in_sync notifies (resolved after failure)", StatusError, StatusInSync, true},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			if got := shouldNotify(tc.prev, tc.new); got != tc.want {
				t.Fatalf("shouldNotify(%q, %q) = %v, want %v", tc.prev, tc.new, got, tc.want)
			}
		})
	}
}